The proposed fiber optic cocaine biosensor is a novel analytical device, that would combine biosensor technology with immunoanalysis, for detection of cocaine and or metabolites in body fluids. The biosensor employs a unique approach, takes only seconds to minutes for the assay, is simple to operate and if successful the principle can be applied to detection of other drugs of abuse, therapeutics, toxicants and endogenous chemicals. Cocaine shall be derivatized and bovine serum albumin-cocaine used as antigen. Monoclonal antibodies (MAb) shall be immobilized on the optic fibers and used as sensing elements for cocaine and metabolites. Cocafluorescein, a fluorescein conjugate of cocaine will be used to generate the optical signal when it binds to the fiber. Cocaine and metabolites would displace the bound cocafluorescein and reduce fluorescence in a concentration-dependent manner. Since the optical signal being monitored is fluorescence emanating in the evanescent zone, but captured by and transmitted through the fiber, the detection system should be transparent to other matrices in the sample such as hemoglobin or cells. There are five specific aims: 1. Synthesize a cocaine antigen and fluorescent probe (cocafluorescein). 2. Raise polyclonal and monoclonal cocaine antibodies and select the most suitable for use in the biosensor. 3. Immobilize anticocaine antibodies on optic fibers and select the concentration of cocafluorescein for use as an optical signal generator. 4. Determine the sensitivity and specificity of the cocaine biosensor. 5. Determine the ability of the biosensor to detect cocaine and metabolites in untreated human blood and urine. With no requirement for pretreatment (e.g. cell and hemoglobin removal) the assay is completed in minutes. An ideal cocaine biosensor should be specific for detecting cocaine and its metabolites that occur in urine and blood and not give false positive or negative, should be highly sensitive (detecting ppt), very rapid and reusable.